Captive balloon



Jan. 22, 1935. J. LETOURNEUR 1,988,562

CAPTIVE BALLOON Filed Nov. 25, 1952 2' sheets-sheet 1 J. LETOURNEUR Jarzz'; 1935.

c GAPTIVE BALLOON Filed Nbv. 2s, 1952 2 Sheets-Sheet 2 Patented Jan. 22, 1935 CAPTIVE Jean Letourneur,

BALLooN Versailles, France Application November 23, 1932, Serial No. 644,054

In France November 27, 1931 v 3 Claims.

Captive balloons which are elongated so as to be stabilized in the wind are provided with ns attached to the rear of the body. These fins are constituted, in general, by air chambers, the outer 5 surface of which is made of an impermeable material and into which air is introduced automatically by means of one or more vents or scoops, placed suitably. The Wind thus maintains a pressure therein under the influence of which the exterior surface tends to acquire a sufficient rigidity for the' fm to fulfill effectively its purpose.

Now it is known thatl the geometrical surfaces that it is possible to obtain with a fabric held taut by an interior pressure are very limited; it is essentialv that, under the actionof said pressure, the surfaces be under tension at every point and in all directions around said point. If a compression should exist at any place the fabric would fold and the surface actually obtained would be entirely different from that calculated. Now the diiculty which is encountered in the calculation of the surfaces having this property is suchthat,

generally, one is restricted to the use of simple surfaces of revolution for whichthe above imperative condition is realized.` If it is necessary to realize other forms, one is led to divide them into sufliciently small elements for eachof them to be considered as a part of a `surface of revolution having this property. lit` is only necessary to choose these surfaces judiciously so that at the lines joining the various elements there will not be objectionable reactions one on the other, which would produce serious deformations. y

Further, to make the fins effective it is important that their lateral exterior surface should offer a great resistance to the wind; for this reason the fins are generally constituted by elements whose surfaces are joined by concave angles; these produce furrows maintained in place by interior connections such as networks of cords, fabric partitions or the like whichfmake the fin very effective.

But on the contrary when the balloon lies in the wind; that is to say is in the normal position, it is necessary that the iin should offer to the wind the least possible resistance. It is known that one of the most favourable conditions for obtaining this result consists, on the one hand, in giving to the body offered to the wind, a surface convex towards the front and on the other hand, in reducing the thickness of this body from the front to the rear in such a way that the streams of air shaped by the front part remain as far as possible tangen- ,tial tothe lateral exterior face of .this body.

" In accordance with the present vinvention an (Cl.v 244-4) iniiatable iin for a captive balloon is composed of elements constituting sections `of surfaces of revolution and isucharacterized. by the fact that all of said elements are substantially tangential to two spaced apart enveloping imaginary surfaces 5 which are developable and also symmetrical with respect to a plane passing through the axis jofthe balloon, and each of which includes a meridianof `the body of the balloon, the radii of the bases of the individual sections decreasing ltowards the rear of the n.

It is well understood as to the line of the aid of the following and with the attached` junction of `two of theseelements that when there is not a common tangent plane at every point of the seam connecting them, the concave angle is maintained in place by a network yof cordsor a partition of fabric suitably pierced withlarge holes for assuring a free circulation -of air in the 1in;V

These fins are applicable to. all captivefballoons but their utilization is particularly advantageous on the balloons with .1obes in which thecross section on a plane Vperpendicular to the axis of the body envelope is,knot acircumference, but a certain number of arcs of a circumference equal or not in size, the -cordsrof whichform a polygon, with extensible sides or not. In such balloons which present otherwise and for certain purposes, particular advantages it is well evidentthat the surface 'comprised between two meridian furrows on which is to..be,inserted a iin is smaller than that'on which the. same '1in would be insertedon a bodyenvelope having the shape of a` body of revolution. 'Towards the rear moreover whenthe linear dimensions of -the sectionsdiminish, Vit lmight be diicultto place a n of consta-ntthickness. On the contrary the use of ns of decreasing' thickness inserted ybetween two-meridians of the envelope iseasy, logical .and advantageous. The invention thus generally described adapted to numerous particular applications to which Vthe protection of this patent application should naturally extend as well as to apparatus utilizing the same method and to their separate parts. Altogether it can be well understood with drawings which it is to be understood/are given only by way of example.

Fig. l represents a lateral elevationand a rear view of a n constructed according to the invention.

Fig. 3 is a Asection through the said iin Figs. 4 and 5 show two further forms o `on the The general form of the n is similar to those which are ordinarily employed; its exterior contour is composed towards the front by an inclined cylindrical surface C connected at the rear with a surface of the general form vof a toroid D. All

the space between the envelope and this contoured surface, which hereafter will be designated by the term horn is lled with portions of cylinders 9frrevolutip-n, the radii of which. decrease towards thetfrearfand-.-which are defined .as -will be seen'below.

To plan the iin, one commences by determining, by taking into account the volume of the balloon, its purpose, its form and so ongthe; general dimensions of the fin and invparticular its length along the meridian of the contour ofthe body envelope and its maximumthickncss. @ne can thus determine the axis of the fhorn -which is composed for example of a line a-b vanda circumferential arc b-c.

. There is; thenconsidered a cylinder .of revolu- 'tionv Garound tnelna ,afb .as .,axis, having for its diameterE the thickness .n xed. vOne determines thenfeasily ,thejntersection of.. thiscylinder with thelbodyenvelopeand .in particular thepoint 1 traced Qnthisenvelopebythe generatrix of the cylinder C situatedin thepla'nevpassing through the aiis l ztb 4and perpendicular to 4the projection Plane i kIt, isfthen possible .to tracethe meridian 1 2 of the envelope passing through the Ypoint 1; this mmeridian is indicated indotted lines on Fig. 1. Qn ;Fig.`2.there'isshown the two meridians k1- 2 .and .'.11.f-.2.1.,SYm.mtriCal relatively t0 the .projection plane.

'.fllell the. symmetrical cylindrical surfacesap- .pii d. `the generatrices are parallel to a-b .are .considered. Iv- Ierenafter `tljiese surfaces are called ,the

cnvclqpesiiriacnnf f lli .elllscrlt thattlieseneratri-x l-S .of the .cylinder .C is common .to `the .envelope VSiinface land .tothe GylintlerC and .that .the two .surfaces .are tangential .fpr the .fiill length of unissen- @ratilx- Fondetermining the theoretioalsllliface of .the

.gutted part!) V.Qf ille..l.iorn,-.one.cnnsider.s .anevery ncintnfthe are li-' a circleliavingitscentre .on ill-Ci thplane .of which .is perpendicular .to tb-c .and of Wliiqh Athe .dinmetcrisequal to Athe distance ...Separating `tine .two .meridians 1-...2 .and 11-21 .catalanes transverse .to the longitudinal axis .and gilicllidingtlle .Successivcpnints considered. ...Then .the .crlvglpe .Surface 0f these circlesisdeterrnined Whsn the .Point .describes the arab-gc. .nissurfaQe Whh lS-ntachd .tnllggrltally to Athe cylinde Czhas generally theiorrn of .a .toroid ,which 'iS tangential l0 the .envelope .Surface along vthe ywhole length o f j the ltwo symmetrical arcs of circles projected from the arc b-c onFig. 1.

i The Ahorn is thus entirely determined.

A .Section 0f thell is than .matleperpendicular *t0 a-1b on a .plane .Stich as 4 5.. The protection of thesection Qfcylinder C isa circle c of which .thti diameter 'is .egual .t0 the maximum thickness. "The PrQJ'StlQn .O f .the intersection lof the same plane with the envelope Asurfarze is composed `of .two .symmetrical .Curves easily determined Yplot- Gills points Qf which the projections .are on the lines 6 7 and 61-71. Then there is traced vafter .the .circle .c a Sericsoi circles. c1 c2, .c3 and so on all tangential to the curi/es 6-'7, 61-f11 and each llilisiiisethg .the foregoing. for .example by a constant angle,l suitably chosen. These circles are nsldeled as transverse `Sttticiis of a series of vcylinders of revolution C1, C2, C3 and so on having their generatrices parallel to a-b. It is evident that all these cylinders are tangential to the Venvelope surface according' to generatrices projected on the axis of these cylinders.

It is sufficient to determine. the intersection of these diierent cylinders on the one hand with the body envelope and on the other hand with ythewtoroidal partof the .horn..iniorder that the .inisentirely dened. l.

In practice it would often be convenient to replace the theoretical toroidal surface of the horn lby truncated cone elements of revolution con- :inectedisuccessively by their bases and having as theirtotal length a dimension at most equal to "the available sizeof the material employed for zthe`aconstruction-1offthe iin; in this latter case,

Atthesetruncated cone elements are no longer theoretically but only practically tangential to the envelope surface. Further by the action of the-interiorJ pressure-.when thef finis. inflated Iwith air, the. true surface would jbavery near thel theoretical toroidal surface .aslongas the lengths of the truncated cone elementsl are very. small.

shouldrbefdisposed perpendicularr to thev plane of -symmetry and at the bottom vof ythe .furrows, v`suitable connectionsfor.example fabric partitions, so that these aappear intheprojection-of the ,section according to the plane 1 -5, the sizes of which :partitions are constant for teach fof them; thesejpartitions, whicharefr-epresented in the Yprojection `at 8--9, :8l- 91 :and .so on are v.pierced withapertures so ,tliatthe air can circulate freely throughthe ,wholepf the-fin.

Finally, 4a .vent or .scoop l10 Asuitably placed according .to the zinclination of the balloon `in ascent permits :the rentryof the iair for inflating .)].'l.(rflIl..v

The .-finthusconstructed is evidently of -decreasing.tlo.ick1f1ess; Fig. .3 shows a-section .on Vthe `planeof line.3-3of Fig. 1 .parallel to the axis .Of .thc= body envelope; ufurther it fulfils the con- .ditions .of the A.principle f claimed; it is composed v elements aretangential to an imaginary surface, in this Y.case cylindrical, including two smeridians voftheenvelope. lFurther lay-arrangingfthe maximu-mthioknessandithe angle'according to which desired its I thickness and the number of "furrows and .thuswithin certain limits its effectiveness and resistance in the wind.

Instead ,of taking aline parallel to -a--b 'for .the ldirection -of the generatrix of ithe `'envelope -surfa ce, one could take anyzother :direotionparallel :to :thepplane .of symmetry, forexample a perpendicular tothexaxis'of the body envelope. In the latter case the front part ofthe horn would no 'longer Ebea cylinderbut a substantially conical ysurface and @the `fur-ro'ws/SS would loe vertical as shown on Fig. which represents the form of a fin thus realized.

Figs. 5 and -6 represent another embodiment in which the` envelope surface is no longer a cylinder but composed of conical surfaces containing as beforetwo .symmetrical meridians of the envelopaand'having for their apexa point S which in the example here described is situated in .the plane Aof symmetry, on the vertical of the front of .the envelope and in an extension of the ,line a-b which is the axis of the front part of .the horn. F.urthenit issupposed here that the body envelope would .not have the form o f a .body of vIt.isrwell understood that in construction: there:e

-of elements of Vsurfaces.,ofrevolution; all these 45 I revolution but would be composed of six equal y the n. The meridians of the envelope passing through the points 21 and 211 are determined and the envelope surface composed of two conical sheets having for their apex the point S and which meet the meridians 21e-22, 211-221,

considered. y

The horn is composed at the front by a truncated cone of revolution T, the axis of which is in the plane of symmetry, the apex of which is at S and of which ageneratrix passes through the point 21, also, at the rear, by a surface of the general form of a toroid D, determined as in the preceding example with the single difference practically that instead of considering the parallels to a--b lines concurrent at S are considered. This surface is evidently tangential to the envelope surface for the whole length of the symmetrical circular arcs projected on the plane of symmetry along b--c.

The space comprised between the envelope and the horn is entirely filled by portions of truncated cones of revolution T1, T2, T3 and so on with apex S, tangential to the envelope surface, for all the length of the generatrices projected on the axes of the cones. The sections f t1, t2, t3 and so on, of the truncated cones T, T1, T2, T3 and so on, intersect on suitably chosen chords; for example the chord common to the sections of the cone T and T1 is seen from the centre of the section t at a certain angle which is the same for similar sections t1, t2 and so on.

It is sufcient then to determine the intersection of these different conical surfaces, on the one hand with the surface of the body envelope and on the other hand with the toroidal surface of the horn for the fin to be entirely xed. In practice one would often replace the theoretical toroidal surface ofY the horn by a series of elements of truncated cones of revolution connected together by their successive bases. In this case the truncated cone elements would not be theoretically but only substantially tangential to the envelope surface. Further, under the action of interior pressure when the fin is inflated by the air, the actual surface would be near to the theoretical toroidal surface as long as the length of these truncated cone elements was very small. Here again, the furrows would be maintained in place by partitions of fabric pierced with large openings perpendicular to the plane of symmetry; these partitions are here trapezoidal, they would be seamed to the edges of the sheets corresponding to the conical surfaces T, T1, T2 and so on. A valve 30 placed suitably permits the inflow of air which inates the fin in ascent.

The iin thus constituted is evidently of de'- creasing thickness; further, itfulls the conditions of the principle claimed; it is composed of elements of surfaces of revolution and all the elements are tangential to a developable surface, conical in this case, which contains two meridians of the envelope. Furtherpthe thickness of this n diminishes away from the envelope and the more rapidly the closer the common apex S of the conical surfaces has been taken to the envelope; one can thus diminish its resistance in the air while maintaining the total surface and the furrows and thus its effectiveness.

` It is obvious that the examples given above are only indicated in order to make the invention understood and to show the diversity of its possible applications; further, they do in no case limit the arrangements which can be realized by the invention.

What I lclaim and desire to secure by Letters Patent of the United States of America is:-

1. An inflatable n fora captive balloon comprising aplurality of elements .constituting sections of surfaces rof revolution and'an inflatable element extending along the outer edge of the 1in and to which each of the individual sections is connected, the said plurality of elements being arranged substantially tangential to two spaced apart enveloping imaginary .surfaces which are developable and also symmetrical with respect to a plane passing through the axis of the balloon and each of which includes a meridian of the body of the balloon, the radii of the bases'of the individual sections decreasing towards the rear of the fm. 2. An inflatable 1in for a captive balloon comprising a plurality of elements constituting sections of surfaces of revolution and an inflatable element extending along the outer edge of the fin, said inflatable element having a conical portion and being curved to the shape of a horn, the said plurality of elements being arranged substantially tangential to two spaced apart enveloping imaginary surfaces which are developable and also symmetrical with respect to a plane passing through the axis of the balloon and each of which includes a meridian of the body of the balloon, whilst the radii of the bases of the individual sections decrease towards the rear of the fin, and said sections have in common with said horn-shaped element and with each of the two spaced apart enveloping imaginary surfaces a common tangent plane, the said horn-shaped element being connected to the balloon surface between the two meridians defining the said spaced apart enveloping imaginary surfaces.

3. An inflatable npfor a captive balloon comprising a pluralityof elements constituting sections of surfaces of revolution and an inflatable element extending along the outer edge of the fin, said inflatable element being partly cylindrical and partlyconical and curved to the shape of a horn, the said plurality of elements being arranged substantially tangential to two spaced apart enveloping imaginary surfaces which are developable and also symmetrical with respect to a plane passing through the axis of the balloon and veach of which includes a meridian of the `body of the balloon, whilst the radii of the bases of the individual sections decrease towards the rear of the fin, and said sections have in common with said horn-shaped element and with'each of the two spaced apart enveloping imaginary surfaces a common tangent plane, one end of the cylindrical portion and one end of the conical portion of the said horn-shaped element being connected to the balloon surface between the two meridians defining the said spaced apart enveloping imaginary surfaces.

JEAN LETOURNEUR. 

